# How does this circuit work?

1. Apr 15, 2017

### Manoj Sahu

I stumbled upon this inverter circuit while searching for the same on internet. Can anyone please explain working of this circuit to me.

2. Apr 15, 2017

### Svein

The CD4047 is connected as an oscillator (frequency determined by19kΩ / 0.22μF). The outputs on pins 10 and 11 are in opposite phase (when one is high, the other is low) and in 50% duty cycle. Therefore the two MOSFETs are turned on alternately, driving the transformer with a square wave. This waveform is amplified through the transformer, creating a 230V square wave.

3. Apr 15, 2017

### Manoj Sahu

Thanks. How do I calculate the current and frequency ?

4. Apr 15, 2017

### Svein

The free-running frequency (taken from the data sheet) is typically 1/(2.2*R*C) = 1/(2.2*19E3* 0.22E-6)Hz ≈ 110Hz. The output frequency is half of that.

5. Apr 15, 2017

### CWatters

The current depends on the load. Note that the output transformer is a 12:230 step up transformer so the current flowing in the FETs is much much higher than the load current. You may well need heatsinks on the FETs and suitably sized conductors/wires and 12v battery.

6. Apr 15, 2017

### Manoj Sahu

If I use two 20w cfl and one 3w led light, will the circuit be able to draw that kind of load? How much power the circuit is capable of drawing?

7. Apr 15, 2017

### Manoj Sahu

As you said that FET's will draw much more current, will it not damage the transformer winding (assuming transformer is rated 12-0-12/230V, 5amp).?

8. Apr 15, 2017

### Manoj Sahu

If I have to get frequency =50.xx Hz assuming that CD4047 is used in Astable mode where Ta=4.40RC, do I have to increase the resistance (+2.5 ohm)/capacitance.

9. Apr 15, 2017

### Manoj Sahu

How do you make an IC to work on 50% duty cycle ?

10. Apr 15, 2017

### CWatters

Thats a very light load. Shouldn't be a problem for that circuit.

11. Apr 16, 2017

### davenn

and just a little bit of advice
Next time post a pic with the correct orientation so everyone doesn't have to kink their neck to read it

12. Apr 16, 2017

### Manoj Sahu

Oh yeah, that I forgot. Thanks for the bit of advice.

13. Apr 16, 2017

### Svein

Run the output through a "toggle" flip/flop.

14. Apr 16, 2017

### Manoj Sahu

Thank you. I have one doubt though. How should I calculate output power ?

15. Apr 16, 2017

### CWatters

You said the load is one 20W cfl and a 3W LED so the load power is 20 + 3 = 23W.

The load current is 23W/230V = 0.1A

The circuit diagram says it can deliver 5A so the load is only 0.1/5 * 100 = 2% of the maximum.

16. Apr 16, 2017

### CWatters

Have you considered using a 12V cfl lamp and a 12V LED instead of 230V ?